1. Field of the Invention
The present invention relates generally to a communication system using a Virtual Router Redundancy Protocol (VRRP), and more particularly, to a router apparatus using Bi-directional Forwarding Detection (BFD) and an operation method therefor.
2. Description of the Related Art
In general, a plurality of hosts, which are connected by a Local Area Network (LAN) and located in a specific area, select one default router and transmit packets through the router, for communication with an external network. The router receives a packet having its destination address, searches for the shortest route to the destination address, and transmits the data packet through the determined route.
However, if a failure occurs in a default router, e.g., due to a power failure, a reboot, scheduling waiting, etc., hosts may lose the route through which they can communicate with an external network. A method proposed as a solution to these problems may include a Virtual Router Redundancy Protocol (VRRP: RFC2338) and a Hot Standby Router Protocol (HSRP: RFC2281).
In a structure using these protocols, when a host uses a fixedly set default router, it has one master router and one or more backup routers. One or more backup routers refer to a backup group, and one of the backup routers is used for the host.
VRRP defines a dynamic selection protocol that dynamically assigns any one of VRRP routers in the LAN as a virtual router. Because every protocol messaging is performed using an Internet Protocol (IP) multicast datagram, VRRP is a protocol that can be universally applied to all networks supporting IP multicast.
In VRRP, a master router periodically sends an advertisement message to inform backup routers that it is in operation or in an active state, and the backup routers may recognize that the master router is in operation, by receiving the advertisement message from the master router. If a failure occurs in the master router, the master router can no longer deliver the advertisement message. Consequently, when a backup router cannot receive the advertisement message, it detects that a failure has occurred in the master router, and because the backup router is qualified as a master router, then takes the place of the master router. The master router and the backup router use the same virtual Identifier (ID) and the same virtual IP address, and each host sets this virtual IP address as an address of a default gateway.
In router redundancy based on the above-described VRRP, a unit period for which a mater router sends an advertisement message to a backup router is one second, and the backup router determines that a failure has occurred in the master router, if it fails to receive an advertisement message from the master router for three seconds.
In VRRP-based router redundancy, providing quick switching from a backup router to a master router is very important to minimize interruption of services. Therefore, there is a need for a method in which a backup router can detect a failure of a master router within a shorter time.